Air conditioning apparatus



Nov. 21, 1961 c. F. ALSING 3,009,335

AIR CONDITIONING APPARATUS Filed April 15, 1960 s C L 56 26 3} Fl G. l 38% I 28 C H C REVERS/NG VALVE I INDOOR COIL a OUTDOOR COIL l---C ,w' I I2 L7 H! J I4 '1 n.

FLOWRESTPlCT/NG MEANS INVENTOR WITNESSES f CARL F. ALSIN'G T ORNEY United States Patent 3,009,335 Am CGNDITIONING APPARATUS Carl F. Alsing, Wilbraham, Mass., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., :1 conporaticn of Pennsylvania Filed Apr. 15, 1960, Ser. No. 22,443 3 Claims. (Cl. 62324) This invention relates to air conditioning apparatus for heating and cooling, especially those having a closed, reversible refrigeration circuit, and more particularly to means for reducing the effective charge of refrigerant in such circuits.

Conventional apparatus of the class set fonth includes an indoor heat exchanger or coil which acts as an evaporator during the cooling operation, and an outdoor heat exchanger or coil which, at the same time, acts as a condenser. Conversely, during the heating operation the direction of refrigerant flow is reversed and the indoor coil acts as a condenser while the outdoor coil acts as an evaporator.

Suitable flow restricting means is connected between the indoor and outdoor coils for the purpose of reducing the pressure, in either direction of flow between the indoor and outdoor coils. Preferably this is accomplished by means of a slender, restricted bore tube, commonly termed a capillary tube in the refrigeration art. For reversing the direction of refrigerant flow a reversing valve is usually employed which serially directs the refrigerant from the compressor through the coils, first through the outdoor coil when cooling an enclosure, or first through the indoor coil when heating an enclosure.

The environmental air coming into contact with the outdoor coil is at a generally lower temperature range during Winter operation than during summer operation, as a result of which refrigerant in the system is subject to lower pressures during winter operationand is therefore less densethan during summer operation. For efficient summer and Winter operation, there is presented the problem of reducing the effective charge in the system resulting from the lower pressures and density of the refrigerant during winter operation; and this is solved by the present invention.

According to the present invention, a refrigerant receiver tank is arranged inthe refrigerant circuit so as to be serially connected by the reversing valve between the outdoor coil and the compressor discharge line during the cooling operation, and between the outdoor coil and the compressor suction line during the heating operation. The receiver tank is of unique construction, comprising a shell or hollow body having suitable flow connections, through tubes or conduits, with the outdoor coil and the reversing valve, both flow connections terminating in an upper region of the tank. Additionally, a restricted passageway is provided which extends between a lower region of the tank and region in the tube connected to the outdoor heat exchanger below the lower region of the tank. The volumetric capacity of the tank is such that the overcharge of liquid refrigerant expected during winter operation will fill the tank to a level below the upper ends of the tubes or conduits, and thus be taken out of circulation. During summer operation, the refrigerant will go back into circulation and entrapped oil will also reenter the system through the passageway. It is also desirable that the ends of the tubes or conduits making flow connections to the tank be spaced apart and out of registry with each other in order to promote the separation of gaseous and liquid refrigerant in the tank.

The foregoing and other objects are eifected by the invention as will be apparent from the following description and claims taken in connection with the accom- 2 panying drawings, forming a part of this application, in which:

FIG. 1 is a diagrammatic view of a reversible refrigeration system embodying the invention; and

FIG. 2 is an enlarged sectional view of a receiver tank shown in FIG. 1.

The invention, as diagrammatically shown, is applied to a reversible refrigeration system or heat pump system including an indoor coil or heat exchanger 10 and an outdoor coil or heat exchanger 12, both of which may be of the conventional cross-finned serpentine type. Although not shown, provision is made for conveying air over the indoor coil 10 and delivering the same to the enclosure to be conditioned. The coil 10 serves as the condenser during heating operation. The outdoor coil 12 is placed in heat transfer relationship with the outside atmosphere and provision is made for conveying air over the coil 12 and then discharging it to the outdoors or to some other place exteriorly of the enclosure. The coil 12 serves as the condenser during cooling operation and as the evaporator during heating operation.

Further included in the system is compression means in the form of a motor compressor unit 14 having a suction line 16 and a discharge line 18, both connected to a reversing valve 20. The reversing valve 20 is adapted to place the compressor suction line 16 and discharge line 18 in communication with the coils 10 and 12, respectively, for cooling the enclosure, and to reverse the connections and place these lines in communication with the coils 12 and 10, respectively, for heating the enclosure. It is the function of the reversing valve 20 to serially direct the refrigerant from the motor compressor 14 through the coils 10 and 12, first through the outdoor coil 12 when cooling an enclosure, or first through the indoor coil 10 when heating the enclosure. In FIG. 1, the direction of refrigerant flow during the cooling operation is indicated by broken line arrows, and solid line arrows indicate the direction of flow during the heating operation. Suitable provision is made for actuating the reversing valve 20, as by a manually movable knob 22.

A flow restrictor, which provides pressure reducing or expansion means, is connected between the indoor coil 10 and the outdoor coil 12; and it preferably comprises a slender, restricted bore tube 24, commonly referred to in the art as a capillary tube.

An overcharge of refrigerant results when the unit is switched over from summer operation to winter operation. This is attributable to the fact that a lower range of outdoor temperatures coming into contact with the outdoor coil 12 produces a lower pressure level in the outdoor coil, resulting in refrigerant being delivered to the motor compressor 14- with a lower specific density. Also, the temperature differential between the indoor and outdoor coils is greater in winter time than during summer time; for example, the temperature diiference between coils during summer operation may average 15 to 20 degrees F., and the same temperature difference during the winter time may average between 25 to 40 degrees F. An increased temperature difference between the coils is accompanied by an increased pressure difference between the coils. In this situation the motor compressor 14 pumps refrigerant through the circuit at a lower rate, weightwise, and, at the same time, the larger pressure difference between the indoor and outdoor coils tends to increase the rate of refrigerant flow through the capillary tube 24. As a result, the indoor coil 10 has a reduced level of liquid refrigerant and the outdoor coil 12 contains an excessive quanity of liquid refrigerant; and sometimes liquid refrigerant floods through to the suction line, and possibly the compressor, causing a condition known as frost-back. Lower efiiciency results when liquid refrigerant flows beyond the evaporator because refrigeration work is performed by components of the refrigeration system which are not in contact with the outdoor air. Also, frost-back to the compressor lowers the temperature of discharge gas delivered to the condenser and thus lowers the efliciency of the system in the compression and condensing stages. It is therefore desirable to avoid the condition known as frost-back by reducing the effective charge of refrigerant in the system by use of a receiver tank 26.

The receiver tank 26 comprises a shell or body 28 into which is admitted a tube 34 which provides communication between the outdoor coil 12 and an upper region in the tank 26. The tube 34 extends upwardly into the tank body 28, through a lower portion thereof, and terminates at an upper region therein. The upper region of the tank 26 also communicates, by a conduit 36, with the reversing valve 20 which, as mentioned previously, is operative to effect a refrigerant flow connection with either the suction line 16 or the discharge line 18 depending, respectively, upon whether the unit is being used to heat or cool an enclosure. Preferably the ends of the tube 34 and the conduit 36 are spaced apart and out of registry with each other so that fluid entering the tank 26 from one of them is not directed into the other before the gaseous refrigerant and liquid refrigerant have had an opportunity to separate. Separation may be further pro moted during the heating operation if the end of tube 34 is bent, as shown, so that refrigerant will flow tangentially and upwardly with respect to the wall of tank 26. The tube 34 is provided with a restricted passageway, in the form of a small aperture 38 in a wall portion of tube 34 adjacent the bottom of tank 26, to permit the escape of entrapped oil from a lower region of the tank during the cooling operation.

Upon switching over from cooling operation to heating operation refrigerant flows upwardly into the tank body 28 through tube 34; and, once inside the tank body 28, liquid refrigerant separates from the gaseous refrigerant and settles in the region between the tube 34 and the tank body 28, while the gaseous refrigerant continues to flow upwardly through the conduit 36 and onto the compressor 14. The volumetric capacity of the tank 26 is suflicient to accommodate a quantity of liquid refrigerant amounting to the expected overcharge in the system during winter operation, without rising above the level of the tube 34.

Upon switching back to cooling operation, hot refrigerant gases entering the tank body 28 from the discharge line 18 promote vaporization of the stored liquid and cause it to reenter the system. However, oil contained in the stored refrigerant, being far less volatile than refrigerant, is not so readily vaporized and would tend to remain in the tank 26 were it not for the opening 38 in tube 34. The opening 38 provides a restricted passageway which permits the oil to drain downwardly, by gravity, from a lower region of the tank 26 into tube 34 and become assimilated into the fluid flowing through the system.

In addition to being attractively simple, the present arrangement has the advantage of being located in the circuit where it can protect most effectively against liquid refrigerant flooding through to the motor compressor 14, thereby eliminating frost-bac While the invention has been shown in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof.

What is claimed is:

1. In air conditioning apparatus for heating and cooling an enclosure, a reversible refrigeration system defining a closed circuit for a volatile refrigerant comprising an outdoor heat exchanger; a tank communicating with one end of said outdoor heat exchanger; an indoor heat exchanger; compression means for said volatile refrigerant; means for serially directing the refrigerant from said compression means through said heat exchangers, first through said outdoor heat exchanger in said one end thereof when cooling said enclosure, or first through said indoor heat exchanger when heating said enclosure; means for expanding the refrigerant in the second heat exchanger through which refrigerant flows after leaving said compression means; a tube providing communication between an upper region in said tank and said outdoor heat exchanger; a conduit providing communication between an upper region in said tank and said directing means; and a restricted passageway extending between a lower region in said tank and a region in said tube which is below the lower region of said tank.

2. Air conditioning apparatus for heating and cooling an enclosure utilizing a volatile refrigerant and comprising: an outdoor heat exchanger; a tank connected at its lower end to one end of said outdoor heat exchanger; an indoor heat exchanger; compression means for said refrigerant; means including flow connections and a reversing valve for serially directing refrigerant from said compression means through said tank and said heat exchangers, first through said tank and next through said outdoor heat exchanger and then through said indoor heat exchanger when cooling said enclosure, or first through said indoor heat exchanger and next through said outdoor heat exchanger and then through said tank when heating said enclosure; means for expanding the refrigerant in the second heat exchanger through which refrigerant flows after leaving said compression means; said flow conneo tions including a tube providing communication between said outdoor heat exchanger and an upper region in said tank, said tube extending upwardly into said tank through a lower portion thereof and terminating at an upper region therein; a portion of said tube inside said tank and adjacent the lower portion thereof having an aperture formed therein providing a restricted passageway between said tank and said tube.

3. In air conditioning apparatus for heating and cooling an enclosure utilizing a volatile refrigerant and comprising: an outdoor heat exchanger; a tank connected to said outdoor heat exchanger; an indoor heat exchanger; compression means for said volatile refrigerant; means for serially directing the refrigerant from said compression means through said heat exchangers, first through said outdoor heat exchanger in said one end thereof when cooling said enclosure, or first through said indoor heat exchanger when heating said enclosure; means for expanding the refrigerant in the second heat exchanger through which refrigerant flows after leaving said compression means; flow connections establishing, with said heat exchangers, said tank, said compression means, said expanding means, and said directing means, a reversible refrigeration system defining a closed series circuit for the volatile refrigerant; said flow connections including a tube connected to said outdoor heat exchanger and extending upwardly into said tank through a lower portion thereof and terminating at an upper region therein; means providing a fluid connection between an upper region in said tank and said directing means; and a restricted passageway extending between said tank and said tube for permitting fluid less volatile than refrigerant to flow by gravity from said tank to said tube and thereby avoid entrapment when said apparatus is cooling the enclosure.

References Cited in the file of this patent UNITED STATES PATENTS Smith Apr. 2, 1957 

